The overall goals of this 4 year research plan are two-fold: (a) to characterize the role of cannabinoid receptors CB1 and CB2 in the modulation of T-cell function by endogenous eicosinoid-like cannabinoids; and (b) to elucidate the signal transduction pathways by which these endocannabinoids disrupt T-cell activation. The significance of this goal is that it will provide direct insight into the role of cannabinoid receptors, and their naturally occurring ligands, in the regulation of both immunologic homeostasis and effector function. To date a number of putative eicosinoid-like cannabinoids have been identified by competitive binding as endogenous cannabinoid receptor ligands. The most extensively characterized with respect to immune modulation are arachidonylethanolamide (anandamide; Ana) and 2-arachidonyl- glycerol (2-Ara-Gl). Both ligands bind to CB1 and CB2 and induce a variety of cannabimimetic responses. At the biochemical level, the most significant similarities include inhibition of adenylate cyclase, repression of DNA binding by certain specific transcription factors critical for leukocyte activation, and the inhibition of IL-2 gene expression. At the cellular level, similarities to plant-derived cannabinoids include suppression of a variety of immunologic responses. Specifically, inhibition of T- cell and B-cell proliferation, decreased recognition of class II MHC (mixed lymphocyte response), and the inhibition of IL-2 secretion. Based on the observations described above, our present investigation will test the hypothesis: Modulation of T-cell activity by endogenous cannabinoid receptor ligands, anandamide and 2-arachidonyl-glycerol, is mediated directly through cannabinoid receptors, CB1 and/or CB2, resulting in disruption T-cell activation. We will test our hypothesis using the following specific aims (SA): In SA#l we will characterize the role of CB l and CB2 in the inhibition of IL-2 expression by Ana and 2-Ara-Gl in activated T-cells. In SA#2 we will characterize the direct effects of Ana and 2-Ara-Gl on the regulation of NF-AT in activated T- cells. In SA#3 we will characterize, in the context of defined activation stimuli: (a) the inhibition of T-cell activation by endocannabinoids; and (b) the temporal relationship between exposure to endocannabinoids and inhibition of T-cell activation. In SA#4 we will characterize the direct effects of Ana and 2-Ara-Gl on PKC and MAP kinase activity.